fix invalid arg handling (io, stdin) and add tests for this

Makefile

@@ -67,6 +67,7 @@ clean:
 
 test:
 	go test -v ./...
+	bash t/test.sh
 
 singletest:
 	@echo "Call like this: ''make singletest TEST=TestPrepareColumns MOD=lib"

lib/io.go

@@ -55,40 +55,54 @@ func ProcessFiles(c *cfg.Config, args []string) error {
 func determineIO(c *cfg.Config, args []string) ([]io.Reader, string, error) {
 	var pattern string
 	var fds []io.Reader
-	var havefiles bool
+	var haveio bool
 
-	if len(args) > 0 {
-		// threre were args left, take a look
-		if _, err := os.Stat(args[0]); err != nil {
-			// first  one is  not a  file, consider  it as  regexp and
-			// shift arg list
+	stat, _ := os.Stdin.Stat()
+	if (stat.Mode() & os.ModeCharDevice) == 0 {
+		// we're reading from STDIN, which takes precedence over file args
+		fds = append(fds, os.Stdin)
+		if len(args) > 0 {
+			// ignore any args > 1
 			pattern = args[0]
 			c.Pattern = args[0] // used for colorization by printData()
-			args = args[1:]
 		}
-
+		haveio = true
+	} else {
 		if len(args) > 0 {
-			// only files
-			for _, file := range args {
-				fd, err := os.OpenFile(file, os.O_RDONLY, 0755)
-
-				if err != nil {
-					return nil, "", err
+			// threre were args left, take a look
+			if args[0] == "-" {
+				// in traditional unix programs a dash denotes STDIN (forced)
+				fds = append(fds, os.Stdin)
+				haveio = true
+			} else {
+				if _, err := os.Stat(args[0]); err != nil {
+					// first  one is  not a  file, consider  it as  regexp and
+					// shift arg list
+					pattern = args[0]
+					c.Pattern = args[0] // used for colorization by printData()
+					args = args[1:]
 				}
 
-				fds = append(fds, fd)
+				if len(args) > 0 {
+					// consider any other args as files
+					for _, file := range args {
+
+						fd, err := os.OpenFile(file, os.O_RDONLY, 0755)
+
+						if err != nil {
+							return nil, "", err
+						}
+
+						fds = append(fds, fd)
+						haveio = true
+					}
+				}
 			}
-			havefiles = true
 		}
 	}
 
-	if !havefiles {
-		stat, _ := os.Stdin.Stat()
-		if (stat.Mode() & os.ModeCharDevice) == 0 {
-			fds = append(fds, os.Stdin)
-		} else {
-			return nil, "", errors.New("No file specified and nothing to read on stdin!")
-		}
+	if !haveio {
+		return nil, "", errors.New("No file specified and nothing to read on stdin!")
 	}
 
 	return fds, pattern, nil

t/test.sh

@@ -0,0 +1,45 @@
+#!/bin/sh
+
+# simple commandline unit test script
+
+t="../tablizer"
+fail=0
+
+ex() {
+    # execute a test, report+exit on error, stay silent otherwise
+    log="/tmp/test-tablizer.$$.log"
+    name=$1
+    shift
+
+    echo -n "TEST $name "
+
+    $* > $log 2>&1
+
+    if test $? -ne 0; then
+        echo "failed, see $log"
+        fail=1
+    else
+        echo "ok"
+        rm -f $log
+    fi
+}
+
+# only use files in test dir
+cd $(dirname $0)
+
+echo "Executing commandline tests ..."
+
+# io pattern tests
+ex io-pattern-and-file $t bk7 testtable.kube
+cat testtable.kube | ex io-pattern-and-stdin $t bk7
+cat testtable.kube | ex io-pattern-and-stdin-dash $t bk7 -
+
+# same w/o pattern
+ex io-just-file $t testtable.kube
+cat testtable.kube | ex io-just-stdin $t
+cat testtable.kube | ex io-just-stdin-dash $t -
+
+if test $fail -ne 0; then
+    echo "!!! Some tests failed !!!"
+    exit 1
+fi

t/testtable

@@ -0,0 +1,6 @@
+NAME                                                 READY   STATUS    RESTARTS       AGE
+alertmanager-kube-prometheus-alertmanager-0          2/2     Running   35 (45m ago)   11d
+grafana-fcc54cbc9-bk7s8                              1/1     Running   17 (45m ago)   1d
+kube-prometheus-blackbox-exporter-5d85b5d8f4-tskh7   1/1     Running   17 (45m ago)   1h44m
+kube-prometheus-kube-state-metrics-b4cd9487-75p7f    1/1     Running   20 (45m ago)   45m
+kube-prometheus-node-exporter-bfzpl                  1/1     Running   17 (45m ago)   54s